In the prior art humidity as such has been measured by capacitive humidity sensors, where the dielectric of the humidity sensor has been sensitive to humidity. By heating also other substances like ammonia have been measured.
Contents of substances like H2O2 (Hydrogen peroxide), ETO (Ethylene Oxide), and O3 (Ozone) have been measured by electrochemical cells or by IR-optical devices. These devices are very complicated or short-lived and thus also expensive.
Thus, there exists a need for improved sensor and method for measuring content of catalytically degradable substances.